Research paper · RP39

Mother Tongue, Bigger Effect?

Do wellbeing programmes work better when they arrive in a participant’s first language? Between-study comparisons put the first-language advantage at about g = 0.28, but fewer than five eligible trials compared the same programme in a first versus a second language, so a new pooled estimate is not yet possible; the number of Indian head-to-head trials is zero. This PRISMA-2020 systematic review asked whether psychological and wellbeing programmes delivered in a multilingual adult’s first language outperform the same kind of programme delivered in a second language. Searches of PubMed, PsycINFO, Scopus, Web of Science, Google Scholar, CTRI, ClinicalTrials.gov and OSF (2000–2026) found no randomised trial that assigned the same programme to first-language versus second-language delivery in multilingual adults. The best available numbers therefore come from language-matching subgroups inside cultural-adaptation meta-analyses. Griner and Smith (2006), across 76 studies and 25,225 participants, reported that programmes in a client’s native language (if other than English) were twice as effective as programmes with no language match described (d = 0.49 versus d = 0.21). Soto and colleagues (2018) updated that picture across 99 studies: overall d = 0.50, falling to 0.35 after publication-bias correction; preferred-language delivery and translated measures both enlarged effects. Hall and colleagues (2016) found culturally adapted programmes beat unadapted versions of the same programme (g = 0.52) but did not find language itself a reliable moderator. Interpreter-mediated comparisons are mixed. Indian programmes of real quality — including the Healthy Activity Programme in Goa — have been delivered in local languages, yet none randomised language of delivery. Certainty that first-language delivery causes better outcomes is low. The practical implication for an Indian workplace programme is simpler than the causal claim: English is the mother tongue of 0.02 per cent of Indians and the office language of almost every professional this platform serves. Matching the language of the rep remains the low-regret design choice while the clean experiment is missing.